Aquarium filter



FIG. 1 is a perspective view of the filter;

FIG. 2 is a top plan view of the filter;

FIG. 3 is a right side elevational view of the filter;

FIG. 4 is a front elevational view of the filter;

FIG. 5 is a rear elevational view of the filter;

FIG. 6 is a left side elevational view of the filter; and,

FIG. 7 is a bottom plan view of the filter.

The broken lines shown in FIGS. 1-7 are for illustrative purpose only and form no part of the claimed design. 

The ornamental design for an aquarium filter, as shown and described. 